Reliable Group Data Delivery (RGDD) is a pervasive traffic pattern in data
centers. In an RGDD group, a sender needs to reliably deliver a copy of data to
all the receivers. Existing solutions either do not scale due to the large number
of RGDD groups (e.g., IP multicast) or cannot efficiently use network bandwidth
(e.g., end-host overlays).

Our analysis reveals that Datacast congestion control works well with small
cache sizes (e.g., 125KB) and causes few duplicate data transmissions (e.g.,
1.19{\%}). Both simulations and experiments confirm our theoretical analysis. We
also use experiments to compare the performance of Datacast and BitTorrent. In a
BCube(4, 1) with 1Gbps links, we use both Datacast and BitTorrent to transmit 4GB
data. The link stress of Datacast is 1.01, while it is 1.39 for BitTorrent. By
using two Steiner trees, Datacast finishes the transmission in 16.9s, while
BitTorrent uses 52s.